[FYI] Power drain on notebook

[Pavel Machek]

Hi!

I played a bit with acpi on my toshiba, and got following figures
(toshiba satellite 4030cdt):

system powered on, disk spinning, backlight on, low brightness	12.8W
high brigtness							+0.8W
no backlight							-4.8W
while(1) loop							+7.2W
disk spindown							-0.5W
disk activity							+2.1W

Toshiba without backlight, idle cpu and disk spun down is        6.9W
Toshiba doing kernel compile takes				22.3W

That's quite a difference, and CPU (300MHz mobile celeron) seems to
take quite a lot of power (even in while(1) loop), which in turn means
that power managment is very important.

BTW compare these numbers with philips velo handheld: 0.4W idle
system, 0.6W with backlight, 1.3W system computing at max, <0.1W
system with slowed down clocks. In this case, CPU is able to take as
much power as the rest of system.

ACPI seems to be much better at saving heat from CPU: it replaces idle
loop and is able to conserve power pretty well. CPU seems to do 10x as
much instructions with APM -- probably due to kapmd design.

								Pavel